Method for purifying mercaptan oils



Jan. 10, 1939.

.|.VA. CAMPBELL. JR., Er A1.

IETHOD FOR PURIFYING MERGAPTAN OILS lll' mkg

N om la A Filed Sept. 25, 1933 IMPM/11p@ g:

Qww Hmmm um .M5956 rma Jan. 1o, 1939 METHOD FOR. PUBIFYING MEBCAPTANOILS Joseph A. Campbell, Jr., Manhattan Beach, and

Theodore Merle Phillips, Lomlta, Calif., assignorl to Union Oil Companyof California. Los Angeles, Calif., a corporation of California.

Application September 25, 1933, Serial No. 690,866

20 Claims. (Ci. 196-29) This invention relates to the rening' ofpetroleum, particularly the removal of mercaptans from hydrocarbon oilssuch as petroleum distillate.

The object of the invention is to provide a simple and emcient procedurefor the elimination or conversion of mercaptans in connection with therefining of gasoline and the like, whereby the well known doctorsweetening procedure may be avoided.

Briefly the invention comprises the addition of elementary sulfur to adistillate to be treated and the treatment of the distillate withcaustic soda or other equivalent alkaline solution in the presence of4the sulfur. The invention includes also the subsequent step oirevivifying the separated' used caustic solution to prepare it forfurther use, by treatment of the caustic with additional quantities ofelementary sulfur for removal or conversion of accumulated materialswhich hinder or entirely inhibit its further effectiveness. Theinvention also includes a third step employed under some conditions oftreating the sulfureted caustic solution where it has been in servicefor a long period of time with a small amount of litharge, thereby againrejuvenating and preparing the caustic solution for further use. Thisaddition of small amounts of litharge speeds up the rate of reaction ofthe sulfureted caustic solution.

Considering the process in greater detail, the treatment according tothis invention ordinarily follows acid treatment of the distillate (e.g. gasoline) according'to any usual or preferred procedure. Inconducting the operation where a mercaptan-containing distillate isbeing treated, a quantity of gasoline (preferably nished gasoline) ispassed through a sulfur cone in order that the gasoline may dissolve adesired quantity oi elementary sulfur, such as iiowers of sulfur. Thegasoline so sulfureted may be introduced into the distillate reilningsystem at any one of several points. For example it may be introducedinto the distillate feed to the acid treater and be carried on throughthe acid treating and subsequent water washing system. Or the sulfuretedgasoline may be introduced to the acid treated distillate after all orpart of the sludge has been separated and before water wash. Or thesulfureted gasoline may be introduced after the water wash either beforethe washed distillate has been passed to a caustic wash or as it isbeing passed to the caustic wash. In any one of these instances thetreated distillatel containing elementary sulfur added through themedium of the sulfureted gasoline (or other sulfureted distillate as thecase may be) is passed to the caustic wash so that the caustic treatmentof the acldtreated distillate takes place in the presence of the addedelementary sulfur. According to this treatment a complete conversion orremoval of the mercaptans is eiected, enough elementary sulfur havingbeen employed for the respective distillate to accomplish this result.

Referring to the accompanying drawing, ,and having reference to gasolineas the raw distillate being treated, the row gasoline feed is suppliedto the system through the line IIJ, acid being supplied through the lineI2. The acidulated gasoline is passed through a mixer I3 and throughsolution settling towers I4 according to any well known procedure. theacid treated gasoline being then water-washed as at tanks I5 and pumpedthence to the caustic washing and settling tank I6, and if desired to acaustic settling. tank l1. The various solutions are withdrawn from thevarious tanks asindicated, the `caustic solution being recirculatedthrough the caustic storage tank I8. Finished gasoline is withdrawn fromthe settling tank I'l, and a portion of this is bypassed to the sulfurcone 2U wherein the desired solution of elementary sulfur takes place.From the sulfur cone the sulfureted finished gasoline is pumped to theraw gasoline being treated through any one of a plurality of supplylines 2l,

22, 23 as indicated, or to any other point of introduction between thefeed line I0 and the point of injection of the gasoline being treatedinto the caustic washing tank I6. Satisfactory treatment is obtainedwhen the sulfureted finished gasoline stream is supplied to any one ofthe indicated points. Preferably, however, the sulfureted gasoline issupplied after the Water-wash and may be rst commingled with therecirculated caustic solution which is pumped by way of line 2li to thestream of gasoline being treated just prior to the passage through themixing coil 25 leading to the tank I6.

The above described caustic treat in the presence of elementary sulfuraccomplishes an almost complete conversion of the mercaptan sulfur sothat the iinished gasoline leaving the caustic settling tank Il is sweetto the doctor test. No plumbite or litharge in any form is required toeffect this conversion. The caustic solution It has been foundsatisfactory also to .treat mercaptan-containing gasolines and similarlight petroleum distillates without any previoim or subsequent acidtreat, the present treatment being adequate for elimination orconversion of the mercaptans. v l

It is to be observed that other points of intro-v duction of thesulfureted gasoline to the gasoline being treated may include supplyingthe sulfureted finished gasoline to the treated gasoline stream aftermingling of the caustic solution with the feed gasoline, as through line30. Similarly, various other points of introduction may be selected withsatisfactory results.

The caustic soda solution after separation from the treated distillatemay be re-used as long as it is effective. VAfter a time however thecaustic solution takes up a sufficient quantity of inhibiting materialsto materially interfere with or completely check its effectiveness. Whenthis condition occurs the interfering materials may be converted orremoved by contacting the alkaline solution directly with additionalquantities of elementary sulfur.- Thereupon the caustic solution sorejuvenated may be further re-used.

In some instances it has been found that where ,the sulfureted causticsolution has been in service for a long period of time, beingcontinuously re-used in connection with the above described rejuvenationby the addition of elementary sulfur to the solution, such old solutionbecomes so affected that satisfactory rejuvenation by means ofelementary sulfur is not accomplished. v It has been found that underthese conditions the life of the solution may be further prolonged bythe addition of a small quantity of litharge to the sulfureted causticsolution. Such, addition of litharge has also been found to conserve theamount of the old caustic solution that must be employed. It is to beunderstood however that up to this point no litharge in the form ofplumbite or otherwise is to be used, only the sulfur being used inconjunction with the caustic.

In connection with the addition of the elementary sulfur to themercaptan-bearing distillate to be treated, it is preferred that thesuliurv be added to the distillate after acid treat and after a waterwash following acid treat, although the other points of introductionhave been found to be satisfactory at least under many conditions. Whilethe use of sulfureted gasoline has been indicated above asbeing themethod by which the sulfur is introduced, it is obvious that other knownor preferred means of effecting the sulfur admixture may be employedsatisfactorily. In connection with the rejuvenation of the causticsolution, it is not necessary that the solution be continuously re-useduntil it becomes largely or entirely ineffective. Instead, sulfur may becontinuously added to the caustic solution supply tank. Likewise afterthis solution becomes quite old and it becomes necessary to addlitharge, or if it is desired to increase the rate of reaction of thecaustic solution, this litharge may be continuously added to the supplytank I8 in the very small quantities necessary to produce the desiredresults. This addition of small amounts of litharge, although far belowthe range necessary for the doctor treat of the distillate,

speeds up the rate of reaction of vthe fresh or sulfureted causticsolution to which the litharge has been added.

`The quantities of sulfur to be added to the dis'- tillate'beingtreated, or to be added to the reused caustic solution, and thequantities of lith- Aamamos arge later to be added to the causticsolution which has been in service for a long period of time, may bereadily determined by those skilled in the art, and will depend to aconsiderable extent upon the nature of the distillate being treated, andalso to some extentupon the character and effectiveness of the preceding'acid treat. Again where the treatment here described is ernployedindependently of any acid treat and-upon a.distillate which has not4been acid treated, the quantities will again vary. However as a specincexample the following is given: A cracked gasoline distillate containing0.035% mercaptans, after being passed through an acid treater and washedwith water, was combined with a stream of finished sulfureted gasolinewhich had been contacted in a sulfur cone to dissolve 0.52% ofelementary sulfur, the sulfureted gasoline being fed at a rate to supply0.65 of a unit of elementary sulfur per unit of mercaptan sulfur in thedistillate. 'I'he treated distillate so sulfureted was then passed to anordinary caustic washing and settling apparatus from which the finishedgasoline was withdrawn.l The settled caustic solution was continuouslyrecirculated through the system by way of its supply tank, whichcontained large quantities of elementary sulfur.

It should be understood in connection with the foregoing that whereparticular reference has been had to the treatment of gasoline usingsulfureted gasoline toaid the elementary sulfur, obviously otherdistillates may be so treated, and the procedure, such as points ofaddition may be varied in any obvious or desirable manner so long as thedesired results may-be obtained. Simpotassium hydroxide or mixtures ofsodium hydroxide may be employed as an equivalent. Thus potassiumhydroxide or mixtures of sodium hydroxide and hydrated lime may beemployed, or hydrated lime alone were so used as to be effective.

We claim:

1. A method for purifying mercaptan oils comprising contacting aquantity of mercaptan-bearing hydrocarbon oil with elementary sulfurandcaustic alkali solution free from litharge to convert the mercaptans,removing the treated oil, contacting the resultant caustic lsolutionwith elementary sulfur and using the caustic solution so sulfureted fortreatment of further quantities of such mercaptan-bearing oils.

2. A method according to claim 1 comprising the additional steps oftreating further quantities of oil until the effectiveness of thesulfureted caustic solution becomes impaired, contacting such impairedsolution with litharge to improve its effectiveness, and employing theso treated caustic solution for treatment of furtherquantities of saidmercaptan-bearing oils.

3. A method for refining petroleum distillates comprising acid treatinga mercaptan-bearing distillate, contacting the acid treated distillatewith caustic solution, in the presence of elementary sulfur free fromand in the absence of litharge, separating the treated distillate fromcaustic, contacting the separated caustic solution with additionalelementary sulfur to restore the effectiveness of the caustic solution,.and continuously re-using the solution.

4. A method for refining petroleum distillates comprising acid treatinga mercaptan-bearing distillate, contacting the acid treated distillatewith caustic solution, in the presence of elementary sulfur initiallyfree from and in the absence of litharge, separating the treateddisanimos tillate from the caustic solution, rejuvenating the separatedcaustic solution by the addition o! elementary sulfur to restore itseectiveness, reusing the rejuvenated solution until sulfur rejuvenationbecomes inadequate, contacting such re-used solution with litharge toimprove the eectiveness of the solution, and using the litharge treatedsolution for further treatment of the mercaptan-bearing distillates.

5. A method of purifying mercaptan-bearing hydrocarbon oils comprisingcontacting the oils with elementary sulfur and caustic solutioninitially free from litharge to convert the mercaptans, removing thetreated oil, contacting the thus separated caustic solution withadditional elementary sulfur, contacting the resultant sulfuretedcaustic solution with litharge to improve the effectiveness of thesolution, and using the caustic solution so sultureted and revivifiedfor treatment of further-quantities, of such mercaptan-bearing oils.

6. A continuous cyclic process for purifying mercaptan-bearing petroleumdistillates which comprises acid treating said mercaptan-bearingdistillates, contacting said acid treated distillate with caustic sodasolution in the presence of sulfur free from and in the absence oflitharge, separating the caustic solution and the puriiied petroleumdistillates, revivifying the said separated caustic solution by theaddition of elementary. sulfur thereto and continuously returning the sorevlvifled solution for treatment oi further amounts of-mercaptan-bearing petroleum distillates.

7. A cyclic process for purifying mercaptanbearing petroleum distillatescomprising acid `treating said distillates, contacting the acid treateddistillate with caustic soda solution in the presence of elementarysulfur initially free from and in the absence of litharge, separatingthe puried distillates from the caustic soda solution, reactivating theseparated caustic soda solution by the addition of elementary sulfurthereto,.contacting the reactivated caustic solution with additionaldistillate until sulfur addition becomes inadequate, separating the lastmentioned distillate from such spent caustic solution, adding to suchseparated spent caustic solution a quantity of litharge to reactivatefurther the aforesaid caustic soda solution and sulfur, and continuouslyreturning the reactivated reagent for treatment o! further amounts ofmercaptan-bearing petroleum distillates.

8. A continuous cyclic process for purifying mercaptanbearinghydrocarbon oils which comprises contacting said oils with elementarysulfur and aqueous caustic solution initially free from litharge toconvert the mercaptans, remov- V ing the puriled oil, contacting theresultant separated caustic solution which has become inactive due tothe presence of materials rasen up from the hydrocarbon oil withelementary sulfur to. reactivate the solution, treating furtherquantities of mercaptan-bearing oil with said reactivated solution,separating the last mentioned oil from the spent previously reactivatedcaustic solution, subsequently contacting said spent caustic solutionwith litharge in an amount substantially below that required to form adoctor solution but sulcient to reviviiy the aforesaid caustic solution,and continuously returning the so revivified solution for treatment offurther amounts of mercaptan-bearing hydrocarbon oils.

9. A continuous cyclic process for refining mercaptan-bearing petroleumdistillates which comprises adding eiementary sulfur to a partiallyspent solution of sodium hydroxide and sulfur tree from litharge whichhas been contacted with a mercaptan-bearing petroleum distillate, andtreating further amounts of said-petroleum distillates with the solutionobtained by the aforesaid addition oi elementary sulfur.

10. A process for revivifying a partially spent solution oi sodiumhydroxide and sulfur tree from litharge which has been previously usedin reiining mercaptan-bearing petroleum distillates comprising addingelementary sulfur to said solution in an amount sumcient to restoreactivity to the treating reagent.

11. A process according to claim l0 comprising the additional step ofadding litharge in an amount substantially below that required to obtaina doctor solution to the solution of caustic soda and sulfur at a timewhen, after continued reuse oi.' the said suliurized caustic solution,the addition of elementary sulfur is no longer adequate in revivifyingthe said solution and treating further quantities of such distillatestherewith.

12. A continuous cyclic process ior refining mercaptan-bearing petroleumdistillates which comprises initially subjecting such distillates to theaction of an aqueous caustic solution and elementary sulfur sumcient torender the solution active and in the absence oi litharge, separatingthe spent caustic' solution from the treated distillate, adding furthersulfur to the separated spent caustic solution to regenerate thesolution, then treating further quantities ot distillate with theregenerated solution, separating' the treated distillate therefrom, thenadding to such separated spent caustic solution a quantity of lithargein an amount less than that required to produce a doctor 'solutionthereby activating said spent caustic solution, and then treatingfurther quantities of distillate therewith.

13. A continuous process for purifying mercaptan-bearing petroleumdistillates which comprises effecting solution o! elementary sulfur inthe distillate, treating the thus sulfurized distillate with a causticalkali solution in the absence of litharge, thereby converting themercaptans, said solution of sulfur in the oil being effected apart fromany sulfur content of the caustic solution, removing the treated oilfrom the resultant caustic solution, introducing elementary sulfur intothe resultant caustic solution and using such sulfur-treated causticsolution to treat further quantities of said mercaptan-bearingdistillate containing elementary sulfur in solution.

14. A continuous process for treating mercaptan-bearing petroleumdistillates which comprises dissolving a quantity of elementary sulfurin a petroleum distillate, commingling said solution with amercaptan-bearing petroleum distillate to sulfurize the latter, treatingthe thus sulfurized mercaptan-bearing petroleum distillate with acaustic alkali solution in the absence of litharge, thereby convertingthe mercaptans, removing the treated distillate from the resultantcaustic solution, introducing elementary sulfur into the resultantseparated caustic solution to regenerate the latter, and using suchregenerated sulfur-treated caustic solution to treat further quantitiesof said sulfurized mercaptan-bearing petroleum distillate.

15. A continuous process according to claim 13 wherein the solution ofelementary sulfur in the mercaptan-bearing distillate is eilected priorto addition of the caustic solution to the distillate.

-16. In the sweetcning of 'mercaptan-bcaring hydrocarbon distillateswith caustic soda and sulfur. the method oi' regenerating the causticsoda solution for repeated re-use which includles.I the step oi addingsulfur thereto, in the absenceof distillate to be sweetened, prior toreuse-oi the solution.

17. In the sweetening o! mercaptan-bearing hydrocarbon distillates withcaustic soda and sulfur, the method o! regenerating the caustic sodasolution for repeated re-use which includes the step of adding sulfurthereto-in the absence of distillate to be sweetened. prior to there-use of the solution until the` solution can no longer be regeneratedby the addition of sulfur only, and then regenerating the solution forfurther reuse by adding litharge thereto in the absence of distillate tobe sweetened.

18. A cyclic process for reilning mercaptanbearing petroleum distillateswhich comprises adding velementary sulfur to a partially spent solutionoi' sodium hydroxide free from litharge which has previously beencontacted with a mercaptan-bearing petroleum distillate in thepresence'of sulfur, and without removing reaction products treatingfurther amounts of said petroleum distillates with the resultantsolution obtained by said sulfur addition.

19. A method according to claim 18 wherein patent No. 2.115,1;05.

lamentan sulfur u dass w um petroleum sistillate before treatment withsaid caustic solution.

20. A continuous process for purifying mercaptan-bearing petroleumdistillata which comprises etlecting solution of elementary sulfur inthe distillate,'initially treating the thus sulfur-v ized distillatewith a caustic alkali solution in the absence ot litharge, therebyconverting the mercaptans, saidsolution of sulfur in the oil beingelected apart from any sulfur content oi' the caustic solution, removingthe treated oil from the resultant caustic solution. introducingelementary sulfur into the resultant caustic solution and using suchsulfur-treated caustic solution to treat further quantities oi.' saidmercaptanbearing distillate `containing elementary sulfur in solution,then treating successive quantities of the sulfurized mercaptan-bearingdistillate with said sulfurized caustic solution until said causticalkali solution becomes inetllcient, then regenerating such causticalkali solution by the addition of small quantities oi' lithargeinsuillcient to form doctor solution, and treating additional successivequantities of said sulfurized mercaptan-bearing petroleum distillatewith said litharge-treated caustic solution.

JOSEPH A. CAMPBELL, Jn. THEODQRE MERLE PHILLIPS.

January 1959 JOSEPH A. CAMPBELL, JR., ET AL.

It is nerebyertified 'that error appears 1n' the printed specificationof thef'above numbered patent requiring correction as follows: Page 1,second column, line 15., for the word "row" read raw; page 2, secondcolumn, line 56, strike out "potassium hydroxide or mixtures of andinsert' instead the syllable and words `iler-ily any caustic solutionotherv than; page 5, first column, line 71,-l claim', before "`caustic""insert spent; and that the said Letters Patent should be read with thiscorrection therein that the same may conform to therecord of the case inthe Patent Office.

signed and sealed this 21st day of Merch., A. D. 1939.

(Seal') Henry Van Arsdale. y

Acting Commissioner of Patents.

